The invention refers to equipment for thermochemical treatment of steels and alloys in gaseous mediums with automatic control.
A nitriding unit for steels and alloys in catalyst-treated ammonia is known that comprises an electric furnace with/without a muffle, an ammonia tank, a gas supply and extraction main line, devices of mixing and proportioning, while a catalyst tank is installed on the gas supply main line to the electric furnace. However it does not include means of indirect process monitoring of iron saturation with nitrogen from the gaseous phase (RF Patent No. 2109080 International Patent Classification C23C8/24 published 20 Apr. 1998).
Means of indirect monitoring of the gaseous phase are known to be used in gas nitriding, ferritic nitrocarburizing and catalytic gas nitriding. However in these means the nitrogen potential is considered to be a ratio of ammonia and hydrogen partial pressures in the furnace atmosphere that in practice does not provide any information on a real situation of the gas nitriding process (Yu. M. Lakhtin etc. Theory and Process of Nitriding. M., “Metallurgy”, 1991, pages 39-55).
Their main disadvantage is use of out-of-date evaluation principles for the gaseous phase in the process of iron diffusion saturation with nitrogen and, consequently, a failure to practically control the process.
A unit for low-temperature gas thermochemical treatment of steels and alloys is known that comprises an electric furnace with a muffle, an ammonia tank, a gas supply and extraction main line, a catalyst tank installed inside the furnace space and a solid electrolytic oxygen sensor of immersion type. A signal of the solid electrolytic sensor and nitrogen content in iron are interrelated. For easy control of the process, the nitrogen potential is proposed to be considered equal to nitrogen concentration in iron when the latter reaches balance with the gaseous phase (Zinchenko V. M. et al. Nitrogen Potential: Current State and Development Concept. M, “Mechanical Engineering”, 2003, pages 40-50).
This engineering solution is the most similar analogue and is taken as a prior art for the claimed unit. The main disadvantage of the prior art is lack of equipment for real-time automatic determination of the nitrogen potential by sensor signals. In this case an operator is to measure sensor signals by oxygen and temperature, to define a nitrogen potential value by nomograms and only thereafter to take a decision on process adjustment.